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As well as the beauty of their beaks, puffins have other amazing characteristics. |
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Puffins, for such a widespread and popular seabird, have managed to keep a lot of their private life shrouded in secrecy. Like swallows, they disappear completely in late summer and do not return from a winter spent on the high seas until the following spring. Where they go remains something of a mystery and even ringing recoveries do not provide much of a clue. However, in the main, puffins breeding in the British Isles spill far out across the North Atlantic - some regularly reach Newfoundland's Grand Banks - or scatter over the depths of the North Sea.
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The feature that distinguishes most - the vivid multi-coloured bill - is also dramatically different outside the nesting season and literally shrinks to a shadow of its summer self. Most of the bill's triangular shape and colour is due to a wafer-like outer sheath, which is regrown each year before the birds return to land. It takes five years for a full set of ridged, coloured bands to develop and experts can tell two, three and four-year-old birds apart based on bill patterns.
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Photographs of puffins with their mouths crammed full of gleaming fish held crossways between both mandibles are the epitome of summer. The first fish to be caught is clamped against the upper mandible with the tongue while the next is pursued underwater. Except for the need to deliver food to the breeding colony, there would normally be no opportunity to see how many are stockpiled in the bill at once. So, for the record, the maximum stands at 62. Sandeels, sprats and the fry of shoaling fish like herring make up the bulk of the catch, yet in wintertime, fish may not figure predominantly on the menu at all. Zooplankton and squid then make up most of the diet.
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Puffins are members of the auk family, a group of seabirds that includes guillemots and razorbills. Each species has paddle-shaped wings that are not very effective in the air. Short wings oblige the birds to employ a fast, whirring action but the trade-off comes when they dive. Like penguins, auks 'fly' underwater and, beating against dense seawater, the stubby wings act like flippers and are ideally shaped to provide propulsion.
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During feeding activities, puffins spend more time below the surface than above it. When not burdened with young to feed they also swallow most food while submerged. Birds fitted with transmitters provide an insight into underwater behaviour. On average, dives are between 10 and 30 metres and most prey is captured from dense schools in mid-water. However, every individual in a group of 10 monitored for nearly two weeks regularly made deep dives of up to 70 metres. Dives lasted around 30 seconds but could extend much longer, right up to two minutes. One bird made 194 dives in 84 minutes, coming to the surface for an average of only three seconds between each dive.
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Puffins breed in burrows that they excavate themselves or commandeer from rabbits. Choice of habitat restricts them to offshore islands or inaccessible headlands that boast grassy slopes underlain by soft soil. In the Arctic, where soil depth is minimal, nesting birds are forced to use rock crevices. They are skilled artisans and dig to a well-conceived plan. The tunnel length is longer than the reach of a human arm - a considerable inconvenience for research biologists - and the single egg is laid in a specially enlarged chamber.
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Throughout the breeding season the species is gregarious but colony attendance is curiously unpredictable. This belies a level of social organisation that is only gradually being understood. Before coming ashore groups assemble in rafts from mid-day onwards. Flocks approach and wheel in cliff updrafts, steadily coming closer to ground level. The birds often perform communal fly-pasts and, like planes above a busy airport, stack themselves in a spiral queue rather than descend haphazardly. Upon landing, breeding adults with food quickly disappear down burrows, which fails to explain the greater number of birds standing in the open. These are a mixture of non-breeders and immatures; the latter follow a hierarchy in a code of colony attendance. Two-year-olds come ashore only during the chick-rearing period and do not enter burrows. Three-year-olds arrive earlier and inspect burrows but do not occupy them. Four-year-olds assume tenancy of any vacant burrows and remain in them for long periods without breeding. Older immatures hang out in 'clubs' with non-breeders and, taken together, form the majority of birds visible on bare ground, rocky outcrops or prominent boulders.
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As if good looks are not enough, puffins also score top marks for their display antics that are all the more comical for being well rehearsed and, at times, involving several birds in concert. With such an elaborate language of gestures it is easy to assume that bill-rubbing, synchronised bowing and a rolling side-to-side 'funny walk' are all part of courtship. Perhaps surprisingly, this is not the case. Courtship leading to pair formation (and mating) takes place on the sea at the beginning of the breeding season. After June, most postures are simply greeting ceremonies between pairs or groups of individuals.
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It has long been believed that puffins desert their chick, allowing hunger to drive it out of the burrow. Research shows that this is a fallacy. Young puffins have the longest fledging period of any auk and are fed by the parents for about seven weeks. They receive food, albeit in lesser amounts, right up to the time they leave the nest chamber, by which stage they are fully-grown and nearly the same weight as an adult.
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Do puffins pair for life and how long do they live? Answering such questions is difficult. Compared to landbirds, seabirds have less natural enemies and tend to be longer-lived. Puffins do not start to breed until they are five or six years old and, based on the return rate of marked individuals at colonies, as many as 96 per cent survive from one year to the next. Data from the Welsh island of Skomer also fixed both the divorce rate and the annual rate of shifting burrows at 8 per cent. So let's not credit them with too many human qualities.
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